Marantz DV4100 User Manual download pdf (Page 102)

IC Descriptions.

GB 46 ASD-19.

– Defect detector: Holds the focus and/or radial control

signal on disc dropouts.

– Speed control: Used during access. With radial actuator

feed forward.

– Focus control: PID controller with wide range adjustable

characteristics.

– Radial control: PID controller with wide range adjustable

characteristics.

– Sledge control: PID controller with wide range adjustable

characteristics and a pulsed sledge controller.

– Laser Low Power: Switches the laser from write back to

read power whenever the device tends to go off-track.

9.5 Input circuits servo

Five out of six of the MACE2 servo inputs can be switched

between diode current inputs (for audio and data application)

and error signal inputs (for recordable applications).

The analogue signals from the diode pre processor are

converted into a digital representation using A/D converters.

9.6 Focus control.

9.6.1 Focus start-up.

To bring the actuator in focus position a triangular shaped

voltage is applied to the actuator to perform a search

movement. When the lens moves from or to the disc, CA

(central aperture) is monitored to reach a certain

programmable absolute level. When this value is CA level is

reached, the FOK signal becomes true and FEn is passed to

the FEn level detector.

At the moment this FEn level is reached the wait for the focus

mode is entered and the focus control loop is enabled to

detect a sign inversion in the FEn signal.

When this zero crossing in this FEn signal is detected, the

loop is closed to function as PID controlled loop and is

switched to the PID mode.

During focus start-up a dither signal is added to the output

signal of the integrator. It prevents the actuator from hitting its

natural resonance. With this technique quantisation, effects

are compensated for during start-up.

9.6.2 Focus Position Control loop.

The focus control loop contains a digital PID controller that

has 5 parameters available to the user. These coefficients

influence the integrating, proportional and differential action

of this PID and a digital low pass filter following the PID. The

fifth coefficient influences the loop gain.

9.6.3 Dropout detection.

This detector can be influenced by one parameter. The FOK

signal will become false and the integrator of the PID will hold

if the CA signal drops below this programmable absolute CA

level. When the FOK signal becomes false, it is assumed as

caused by a black dot in the first place.

9.6.4 Focus Loss detection and Fast restart.

Whenever FOK is false longer than about 2 ms, it is assumed

that the focus point is lost. A fast restart procedure is initiated

which is capable of restarting the focus loop within 200 to 300

ms depending on the uP-programmed coefficients.

9.6.5 Focus Automatic Gain Control loop.

The loop gain of the focus control loop can be corrected

automatically to eliminate tolerances in the focus loop. This

gain control injects a signal into the loop that is used to

correct the loop gain. Since this decreases the optimal

performance, the gain control should only activated shortly

(for instance when starting a new disc).

9.7 Radial control.

The MACE2 digital controller includes the following radial

servo functions:

9.7.1 Level initialisation:

During start-up an automatic adjustment procedure is

activated to set the values of the radial error gain, offset and

satellite sum/MIRN signal gain for TPI level generation. The

initialisation procedure runs in a radial open loop situation

and is < 200 ms. This start-up time period may coincide with

the last part of the turntable motor start-up time period.

9.7.2 Automatic gain adjustment:

Because of this initialisation the amplitude of the RE signal is

adjusted within _10% around the nominal RE amplitude.

Offset adjustment: The additional offset in RE due to the

limited accuracy of the start-up procedure is less than +/-

50nm.

9.7.3 TPI level generation:

The accuracy of the initialisation procedure is such that the

duty cycle range of TPI becomes 0.4 < duty cycle < 0.6.

Sledge home:

Sledge moves to reference position at the inner side of the

disc with user defined voltage.

Tracking control:

The actuator is controlled using a PID loop filter with user

defined coefficients.

Access:

In Mace2 there are two fundamentally different ways to

perform an access:

Using the PCS

A more detailed description of this access method is given in

an other section.

Using the servo controlled access:

The way it was done in the predecessors of Mace2.This

access procedure is divided into 3 different modes,

depending on the requested jump size:

access type size access speed

Actuator jump decreasing velocity

Sledge jump maximum power to sledge 1

Controlled sl. jump controlled brake power

The access procedure makes use of a track counting

mechanism, a velocity signal based upon the number of

tracks passed within a fixed time interval, a velocity setpoint

calculated from the number of tracks to go and a user

programmable parameter indicating the maximum sledge

performance.

If the number of tracks to jump is too large, then the Sledge

jump mode is activated, else the actuator jump is performed.

The requested jump size together with the required sledge

braking distance at maximum access speed defines the

value of the maximum numbers of tracks.

During the actuator jump mode, velocity control with a PI

controller is used for the actuator. The sledge is then

continuously controlled using the filtered value of the

integrator contents of the actuator. All filter parameters (for

actuator and sledge) are user programmable.

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Marantz DV4100 User Manual Page 102

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